Evaluation of an Immunoassay-Based Algorithm for Screening and Identification ofGiardiaandCryptosporidiumAntigens in Human Faecal Specimens from Saudi Arabia

Abstract

An immunoassay-based algorithm, involving three commercial kits, was introduced and evaluated for screening and identification ofGiardia/Cryptosporidiumantigens in human stool specimens. Initially,Giardia/CryptosporidiumChek kit (TechLab), an enzyme-linked immunosorbent assay (ELISA), was adopted for screening. The ELISA-positive reactions were subsequently characterised by RIDA QuickGiardiaand RIDA QuickCryptosporidiumimmunochromatographic kits (R-Biopharm). A gold standard test comprising PCR and microscopy was used for preparing control samples. Performance of individual kits was tested against these samples which included 50Giardia-positive, 40Cryptosporidium-positive, and 70Cryptosporidium/Giardia-negative. ForCryptosporidium, specificities of the ELISA and RIDA QuickCryptosporidiumkits were 95.71% and 100%, respectively. Both kits demonstrated sensitivity of 95%. ForGiardia, the ELISA and RIDA QuickGiardiakits showed sensitivities of 100% and 97.5%, respectively. Specificities obtained by the ELISA and RIDA QuickGiardiawere 95.7% and 100%, respectively. Based on the results of two reference PCRs, on 250 random samples, the algorithm exhibited sensitivity, specificity, positive predictive value, and negative predictive value of 97.06%, 100.00%, 100.00%, and 98.91%, respectively. In conclusion, this immunoassay-based algorithm can be used as routine test in diagnostic laboratories for screening and identification of a large number of samples.